Digital inkjet printing of signs and other graphic arts applications is increasingly replacing screen printing and other analog printing technologies. Digital inks for large format printing should provide good image quality, durability, and permanence. While many of the inks in use are solvent-based, in recent years efforts have been made to replace organic solvent-based inks with water-based inks. However, many of the media substrates are nonporous coated papers or polymer films such as vinyl, which presents challenges with respect to water-based inks.
More specifically, nonporous media present wetting and image quality control issues for aqueous inks due to a combination of low media surface energies and low porosity. On nonporous media, droplet coalescence and subsequent ink flow leads to image quality defects, such as intercolor bleeding and mottled area fill non-uniformities. Various surfactant additives have been used previously in order to effectively wet low surface energy media and control image quality defects, such as color-to-color bleed and area fill mottle. These additives are used in an attempt to provide desired wetting properties and to perform well in a high-speed thermal or piezo printhead.
Materials that have been used include nonionic fluorosurfactants with perfluorinated chains of C8 or larger, but these materials are increasingly being replaced with short-chain analogs due to stewardship concerns (C6 or lower). One drawback of the short-chain materials is that the lower hydrophobicity typically provides poorer wetting and image quality control in inkjet printing than traditional longer-chain perfluorinated materials, and this ultimately limits the throughput of high-speed inkjet printing. Thus, the development of specific additives and ink formulations that improve image quality control would be an advancement in the art.